Methods of operating semiconductor memory devices including magnetic films having electrochemical potential difference therebetween

ABSTRACT

Provided are a multi-purpose magnetic film structure using a spin charge, a method of manufacturing the same, a semiconductor device having the same, and a method of operating the semiconductor memory device. The multi-purpose magnetic film structure includes a lower magnetic film, a tunneling film formed on the lower magnetic film, and an upper magnetic film formed on the tunneling film, wherein the lower and upper magnetic films are ferromagnetic films forming an electrochemical potential difference therebetween when the lower and upper magnetic films have opposite magnetization directions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic film structure using a spincharge, a method of manufacturing the same, a semiconductor memorydevice having the same, and a method of operating the semiconductormemory device.

2. Description of the Related Art

The degree of integration of semiconductor devices has rapidly increasedas semiconductor technologies have been developed. An idealsemiconductor device has a high degree of integration and low powerconsumption, operates at high speed and is nonvolatile. A conventionalsemiconductor device may have high power consumption and therebygenerate significant heat. As the semiconductor device generates heat,the operation speed thereof rapidly decreases. To solve this drawback, asuperconductor may be used, but this is applicable only in a limitedfield.

Meanwhile, in connection with nonvolatile memory devices, flash memoryhas been widely used. In addition; as MRAM and SONOS memories have beendeveloped, the nonvolatility of semiconductor memories has beenimproved.

Unfortunately, the characteristics of the conventional semiconductordevice are still far from ideal. Accordingly, a semiconductor devicehaving better characteristics is required. In this regard, an improvedsemiconductor device using electron spin is provided herein.

SUMMARY OF THE INVENTION

The present invention is therefore directed to a multi-purpose magneticfilm structure using spin charge, a method of manufacturing the same, asemiconductor device having the same, and a method of operating thesemiconductor device, which substantially overcome one or more of theproblems due to the limitations and disadvantages of the related art.

It is therefore a feature of an embodiment of the present invention toprovide a multi-purpose magnetic film structure having ferromagneticfilms capable of forming an electrochemical potential differencetherebetween.

At least one of the above and other features and advantages of thepresent invention may be realized by providing a multi-purpose magneticfilm structure including a lower magnetic film, a tunneling film on thelower magnetic film, and an upper magnetic film on the tunneling film,wherein the lower and upper magnetic films may be ferromagnetic filmsforming an electrochemical potential difference therebetween when thelower and upper magnetic films have opposite magnetization directions.

The upper magnetic film may include first and second ferromagnetic filmson the tunneling film, and a magnetization direction of the firstferromagnetic film may be fixed in a direction by the secondferromagnetic film. The upper magnetic film may be a half-metalferromagnetic film, which may be completely spin-polarized by a magneticfield. The multi-purpose magnetic film structure may also include acapping layer on the upper magnetic field.

The lower magnetic film may include a first ferromagnetic filmcontacting the tunneling film and a second ferromagnetic film under thefirst ferromagnetic film. The lower magnetic film may be a half-metalferromagnetic film, which may be completely spin-polarized by themagnetic field. The multi-purpose magnetic film structure may alsoinclude a seed layer under the lower magnetic film. The multi-purposemagnetic film structure may have a size of less than 100² μm².

At least one of the above and other features and advantages of thepresent invention may be realized by providing a method of manufacturinga multi-purpose magnetic film structure, including forming an oxide filmon a substrate, forming a lower magnetic film on the oxide film, thelower magnetic film having a spin polarization ratio, forming atunneling film on the lower magnetic film, forming an upper magneticfilm on the tunneling film, wherein the upper magnetic film has adifferent spin polarization ratio from the lower magnetic film, forminga capping layer on the upper magnetic film, and patterning the cappinglayer, the upper magnetic film, the tunneling film, and the lowermagnetic film.

A seed layer may be further formed on the oxide film before the formingof the lower magnetic film. The forming of the lower magnetic film mayinclude depositing a ferromagnetic film having a higher spinpolarization ratio than the upper magnetic film on the oxide film. Theforming of the lower magnetic film may also include maintaining thesubstrate with the oxide film at a temperature of at least about 500° C.while depositing the ferromagnetic film having a higher spinpolarization ratio than the upper magnetic film on the oxide film.

The upper magnetic film may be formed by sequentially depositing twoferromagnetic films and may be formed with a half-metal ferromagneticfilm having a spin polarization ratio of 80% to 100%. The lower magneticfilm may be formed with a half-metal ferromagnetic film having a spinpolarization ratio of 80% to 100%. The lower magnetic film may be formedusing a ferromagnetic film having a lower spin polarization ratio thanthe upper magnetic film, and may be formed by depositing twoferromagnetic films.

At least one of the above and other features and advantages of thepresent invention may be realized by providing a semiconductor memorydevice including a substrate, a switching element formed on thesubstrate; and a data storing unit connected to the switching element,the data storing unit including a lower magnetic film, a tunneling filmformed on the lower magnetic film; and an upper magnetic film formed onthe tunneling film, wherein the lower and upper magnetic films areferromagnetic films forming an electrochemical potential differencetherebetween when the lower and upper magnetic films have oppositemagnetization directions.

At least one of the upper and lower magnetic films may be a half-metalferromagnetic film, and the data storing unit may have a size of lessthan 100 μm².

At least one of the above and other features and advantages of thepresent invention may be realized by providing a method of operating asemiconductor memory device, the semiconductor memory device having asubstrate, a switching element formed on the substrate, and a datastoring unit connected to the switching element, the data storing unithaving a lower magnetic film, a tunneling film and an upper magneticfilm that are sequentially deposited, the lower and upper magnetic filmsbeing ferromagnetic films forming an electrochemical potentialdifference therebetween when the lower and upper magnetic films haveopposite magnetization directions, wherein, in a state where theswitching element is turned off, a magnetic field is applied to the datastoring unit in a given direction to record data in the data storingunit.

In a state where the switching element is turned on, an offset voltageof the data storing unit may be measured to read data from the datastoring unit. Data recorded in the data storing unit may be read by afirst process of applying the magnetic field to the data storing unitsuch that the upper and lower magnetic films have the same magnetizationdirection in the state where the switching element is turned on, and asecond process of sensing whether or not a current of more than apredetermined value flows through the data storing unit.

In the case where the current of more than the predetermined value issensed, a magnetization state of one of the upper and lower magneticfilms whose magnetization state is varied through the first process maybe restored to the original state. A magnetic field having an oppositedirection to the magnetic field applied in the first process may beapplied to the magnetic film whose magnetization state is varied throughthe first process to restore the magnetization state of the magneticfilm to the original state.

In the state where the switching element is turned off, the upper andlower magnetic films may be allowed to have the same magnetizationdirection to erase data from the data storing unit.

Since the present invention may reduce a device driving voltage to aboutseveral millivolts, power consumption may be reduced and heat generateddue to the power consumption may also be reduced. Therefore, a deviceoperation speed may be also increased. Since the magnetic film structuremay have a very small size, the degree of integration of a deviceemploying the same may be increased. Furthermore, since the magneticfilm structure can have its own potential difference, the magnetic filmstructure may be used for a battery.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present inventionwill become more apparent to those of ordinary skill in the art bydescribing in detail exemplary embodiments thereof with reference to theattached drawings in which:

FIG. 1 illustrates a cross-sectional view of a magnetic film structureaccording to an embodiment of the present invention;

FIG. 2 ‘illustrates a graph of resistance variation of a magnetic filmstructure when a bias voltage applied to the magnetic film structure ofFIG. 1 varies from −0.6V to +0.6V;

FIG. 3 illustrates a graph of resistance variation of the magnetic filmstructure of FIG. 1 at a bias voltage (−0.2 mV to +0.3 mV), at which aresistance and a magneto-resistance ratio are asymmetric;

FIG. 4 illustrates a graph of resistance variation depending on amagnetic field of the magnetic film structure of FIG. 1 at a point P1 ofFIG. 3;

FIG. 5 illustrates a graph of resistance variation depending on amagnetic field of the magnetic film structure of FIG. 1 at a point P2 ofFIG. 3;

FIG. 6 illustrates a graph of resistance variation depending on amagnetic field of the magnetic film structure of FIG. 1 at a point P3 ofFIG. 3;

FIG. 7 illustrates a graph of resistance variation depending on amagnetic field of the magnetic film structure of FIG. 1 at a point P4 ofFIG. 3;

FIG. 8 illustrates a graph of resistance variation of the magnetic filmstructure of FIG. 1 depending on a magnetic field when a plurality ofbias voltages is respectively applied;

FIG. 9 illustrates a graph of resistance variation of the magnetic filmstructure of FIG. 1 depending on a magnetic field at a bias voltage of55 mV;

FIGS. 10 and 11 illustrate cross-sectional views of stages in a methodof applying a bias voltage to the magnetic film structure of FIG. 1;

FIG. 12 illustrates a graph of current-voltage characteristic of themagnetic film structure of FIG. 1 to which a bias voltage is applied, asillustrated in FIG. 10;

FIG. 13 illustrates a graph of a current-voltage characteristic of themagnetic film structure of FIG. 1 to which a bias voltage is applied, asillustrated in FIG. 11;

FIG. 14 illustrates a curve of a current-voltage characteristic of themagnetic film structure of FIG. 1 having a lower magnetic film(half-metal ferromagnetic layer) that is formed under a second condition(20 mTorr, 600° C.) and having a size of 10 μm×10 μm;

FIG. 15 illustrates a curve of a current-voltage characteristic of themagnetic film structure of FIG. 1 having a lower magnetic film(half-metal ferromagnetic layer) that is formed under a second condition(20 mTorr, 600° C.) and having a size of 30 μm×30 μm;

FIG. 16 illustrates a curve of a current-voltage characteristic of themagnetic film structure of FIG. 1 having a lower magnetic film(half-metal ferromagnetic layer) that is formed under a second condition(20 mTorr, 600° C.) and having a size of 50 μm×50 μm;

FIG. 17 illustrates a curve of a current-voltage characteristic of themagnetic film structure of FIG. 1 having a lower magnetic film(half-metal ferromagnetic layer) that is formed under a second condition(20 mTorr, 600° C.) and having a size of 100 μm×100 μm;

FIG. 18 illustrates a curve of a current-voltage characteristic of themagnetic film structure of FIG. 1 to which a resistor is connected;

FIG. 19 illustrates a graph of variation of an offset voltage dependingon the variation of an absolute temperature in a magnetic film structureof FIG. 1;

FIG. 20 illustrates a cross-sectional view of the magnetic filmstructure of FIG. 1 with a lower magnetic film and an upper magneticfilm being reversed;

FIGS. 21 and 22 illustrate stages in a method of manufacturing themagnetic film structure of FIG. 1;

FIG. 23 illustrates a transmission electron microscopy (TEM) image of auniform thickness of a tunneling film of the magnetic film structure ofFIG. 1 formed through the manufacturing method shown in FIGS. 21 and 22;

FIG. 24 illustrates a cross-sectional view of a magnetic RAM accordingto the present invention in which the magnetic film structure of FIG. 20is used as a magnetic tunnel junction (MTJ) layer;

FIG. 25 illustrates a cross-sectional view of a MTJ layer in whichmagnetic films have the same magnetization direction on and under atunneling film in the magnetic RAM of FIG. 24;

FIG. 26 illustrates a cross-sectional view of a MTJ layer in whichmagnetic films have opposite magnetization directions to each other onand under a tunneling film in the magnetic RAM of FIG. 25; and

FIG. 27 illustrates a cross-sectional view of an example of the magneticfilm structure of FIG. 1 used as a magnetic sensor.

DETAILED DESCRIPTION OF THE INVENTION

Korean Patent Application No. 10-2004-0060719, filed on Jul. 31, 2004,in the Korean Intellectual Property Office, and entitled: “MAGNETIC FILMSTRUCTURE USING SPIN CHARGE, METHOD OF MANUFACTURING THE SAME,SEMICONDUCTOR DEVICE HAVING THE SAME, AND METHOD OF OPERATING THESEMICONDUCTOR DEVICE,” is incorporated by reference herein in itsentirety.

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof the invention are shown. The invention may, however, be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. In thefigures, the dimensions of layers and regions are exaggerated forclarity of illustration. It will also be understood that when a layer isreferred to as being “on” another layer or substrate, it can be directlyon the other layer or substrate, or intervening layers may also bepresent. Further, it will be understood that when a layer is referred toas being “under” another layer, it can be directly under, and one ormore intervening layers may also be present. In addition, it will alsobe understood that when a layer is referred to as being “between” twolayers, it can be the only layer between the two layers, or one or moreintervening layers may also be present. Like reference numerals refer tolike elements throughout.

FIG. 1 illustrates a cross-sectional view of a magnetic film structureaccording to an embodiment of the present invention. A magnetic filmstructure having a spin charge caused by an electrochemical potentialdifference of an electron spin state will first be described. Themagnetic film structure 30 of FIG. 1 may have vertical and horizontallengths of about 10 μm, although the vertical and horizontal lengths maybe larger or smaller than 10 μm. The magnetic film structure 30 mayinclude a lower magnetic film 42, a tunneling film 44 and an uppermagnetic film 45. A seed layer 40 may be provided under the lowermagnetic film 42 and a protection capping layer 49 may be provided onthe upper magnetic film 45.

The lower magnetic film 42 may be formed under a first condition (20mTorr, 500° C.) and may have a first electron spin state density. Thelower magnetic film 42 may be, e.g., a Heusler alloy or a half-metalferromagnetic layer, e.g., a Co₂MnSi layer, all electrons of which maybe spin-polarized in a predetermined direction when an external magneticfield is applied. The lower magnetic film 42 may also be formed of otherferromagnetic layers that are equivalent to a Heusler alloy or ahalf-metal ferromagnetic layer. Where the lower magnetic film 42 is aCo₂MnSi layer, it may have a thickness of about 47 nm, but may have alarger or smaller thickness than 47 nm. Where the lower magnetic film 42is a different half-metal ferromagnetic layer, the lower magnetic film42 may have a thickness of 47 nm or a different thickness.

A solid-line arrow illustrated in the lower magnetic film 42 denotes amagnetization direction, i.e., a spin polarization direction, of thelower magnetic film 42, caused by an external magnetic field. Adotted-line arrow denotes the magnetization direction of the lowermagnetic film 42 when the external magnetic field has an oppositedirection.

The tunneling film 44 may have a predetermined thickness through whichelectrons can tunnel. For example, the tunneling film 44 may be analuminum oxide layer (AlO_(x)) and may have a thickness of about 2 nm.The tunneling film 44 may be an insulating layer, rather than an oxidelayer, and may have a different thickness from an oxide layer.

The upper magnetic film 45 may include first and second ferromagneticlayers 46 and 48, which may be deposited sequentially. The firstferromagnetic film 46 may be a pinned layer having a second electronspin state density, in which the magnetization direction or the spinpolarization direction of the electrons is fixed in a given direction.In the first ferromagnetic film 46, the electrons may be spin-polarizedin the predetermined direction in the same manner as the lower magneticfilm 42. However, all the spin polarizations of the electrons of thefirst ferromagnetic film 46 do not have the same direction, in contrastto those of the lower magnetic film 42. In other words, most ofelectrons of the first ferromagnetic film 46 are spin-polarized in thepredetermined direction, but some electrons are spin-polarized in adirection opposite to the predetermined direction.

The external magnetization direction of the first ferromagnetic film 46is a spin polarization direction, with which most of electrons of thefirst ferromagnetic film 46 are aligned. The arrow illustrated in thefirst ferromagnetic film 46 denotes the magnetization direction of thefirst ferromagnetic film 46, i.e., the spin polarization of most of theelectrons of the first ferromagnetic film 46. The first ferromagneticfilm 46 may be magnetized in the arrow direction shown in the drawings,but a minority of the electrons of the first ferromagnetic film 46 mayhave an opposite magnetization direction (not shown). The firstferromagnetic film 46 may be a cobalt iron (CoFe) layer.

The second ferromagnetic film 48 may be an antiferromagnetic layer,which may be a pinning layer for pinning the magnetization direction ofthe first ferromagnetic film 46. The second ferromagnetic film 48 maybe, e.g., an iridium manganese (IrMn) layer of a predeterminedthickness. The first ferromagnetic film 46 may be pinned by the secondferromagnetic layer 48 through exchange coupling. Accordingly, the firstand second ferromagnetic films 46 and 48 may have the same magnetizationdirection. When the second ferromagnetic film 48 is an IrMn layer, itmay have a thickness of about 15.5 nm, although other thicknesses may besuitable, and different thicknesses may be used for different materials.

The capping layer 49 may prevent the second ferromagnetic film 48 frombeing oxidized and may be formed of, e.g., ruthenium (Ru) having athickness of about 60 nm. The seed layer 40 may be provided under thelower magnetic film 42 to promote the growth of the lower magnetic film42 and may include, e.g., a tantalum (Ta) layer having a thickness ofabout 42 nm and a ruthenium (Ru) layer having a thickness of about 9.5nm, sequentially deposited.

When the lower magnetic film 42 and the first ferromagnetic film 46 havea different electron spin state density and the tunneling film 44 isinterposed between and makes contact with the lower magnetic film 42 andthe first ferromagnetic film 46, an electrochemical potential differenceis generated between the lower magnetic film 42 and the firstferromagnetic film 46. The electrochemical potential difference causesthe electrons of the first ferromagnetic film 46, which are in a spindown state, to pass through the tunneling film 44 and move to the lowermagnetic film 42. At this time, the electrons of the first ferromagneticfilm 46 are changed in a spin up state. The movement of electrons fromthe first ferromagnetic film 46 to the lower magnetic film 42 stores anegative (−) charge at an interface of the lower magnetic film 42 andthe tunneling film 44 and stores a positive (+) charge at an interfaceof the first ferromagnetic film 46 and the tunneling film 44.Accordingly, the electrochemical potential difference is generatedbetween the lower magnetic film 42 and the first ferromagnetic film 46.

A predetermined external offset voltage may be applied to the magneticfilm structure 30 to eliminate the electrochemical potential difference.Accordingly, a measured current value of the magnetic film structure 30may be zero at the offset voltage. Since the potential differencebetween the lower magnetic film 42 and the first ferromagnetic film 46may be eliminated when the offset voltage is applied, the potentialdifference may be determined by measuring the offset voltage, since thepotential difference is caused by the electrochemical potentialdifference between the lower magnetic film 42 and the firstferromagnetic film 46.

Also, since the potential difference exists within the magnetic filmstructure 30, charges may be extracted from the magnetic film structure30. Accordingly, the magnetic film structure 30 may be used as a powersource.

The potential difference existing within the magnetic film structure 30is caused by opposite magnetization directions of the lower magneticfilm 42 and the first ferromagnetic film 46. Also, since the magneticfield may be applied externally to determine the magnetization directionof the lower magnetic film 42, the magnetic film structure 30 may beintegrated and used as a rechargeable power source, that is, as asecondary cell. In the example where the magnetic film structure 30 isused as the power source, an integrated unit having a plurality ofmagnetic film structures 30 serially connected with one another may beused as the power source. Further, the integrated unit may be alsoconnected in parallel and constructed as the power source.

Alternatively, in the example where the magnetic film structure 30 isused as the power source, the magnetization direction of the lowermagnetic film 42 may be exchanged by an external magnetic field.Therefore, after the magnetic film structure 30 is charged, that is,after the magnetic field is applied to the lower magnetic film 42 toallow the lower magnetic film 42 to have the opposite magnetizationdirection to the first ferromagnetic film 46, a magnetic field shieldingunit (not shown) may be provided at an external and/or internal of themagnetic film structure 30 such that a magnetization state of the lowermagnetic film 42 is not influenced by the external magnetic field. Themagnetic field shielding unit may be removed to recharge the magneticfilm structure 30.

A physical characteristic of the magnetic film structure 30 illustratedin FIG. 1 will next be described with reference to the attacheddrawings. FIG. 2 illustrates graphs of resistance variation of amagnetic film structure where a bias voltage, applied to the magneticfilm structure of FIG. 1, varies from −0.6V to +0.6V. In FIG. 2, a graphG1 represents a resistance variation of the magnetic film structure ofFIG. 1 when the lower magnetic film 42 has an opposite magnetizationdirection to the first ferromagnetic film 46. A graph G2 represents aresistance variation of the magnetic film structure of FIG. 1 when thelower magnetic film 42 has the same magnetization direction as the firstferromagnetic film 46. A graph G3 represents the variation of themagneto-resistance ratio of the magnetic film structure of FIG. 1. Asmay be seen from graphs G1, G2 and G3, the resistances and themagneto-resistance ratio of the magnetic film structure of FIG. 1 varygreatly when the bias voltage is about zero.

FIG. 3 illustrates in greater detail the resistances and themagneto-resistance ratio of the magnetic film structure of FIG. 1 whenthe bias voltage is about zero. FIG. 3 illustrates a graph of resistancevariation of the magnetic film structure of FIG. 1 at a bias voltagechanging from +0.3 mV to −0.2 mV, at which a resistance and amagneto-resistance ratio are asymmetric. In FIG. 3, reference symbol“□”, R(P), represents a variation of a resistance (hereinafter, referredto as “first resistance”) when the lower magnetic film 42 of themagnetic film structure of FIG. 1 has the same magnetization directionas the first ferromagnetic film 46. Reference symbol “∘”, R(AP),represents a variation of a resistance (hereinafter, referred to as“second resistance”) when the lower magnetic film 42 has the oppositemagnetization direction to the first ferromagnetic film 46. Referencesymbol “Δ”, MR, represents a variation of the magneto-resistance ratio.

Referring to FIG. 3, the first and second resistances and themagneto-resistance ratio exhibit variation at the bias voltage between 0mV and 0.1 mV (100 ηV). In detail, as the bias voltage reaches 0.1 mV,the first and second resistances R(P), R(AP), and the magneto-resistanceratio MR of the inventive magnetic film structure slowly increase. Then,as the bias voltage passes 0.1 mV, the second resistance R(AP) and themagneto-resistance ratio MR begin to rapidly increase. However, thefirst resistance R(P) of the magnetic film structure 30 does not varygreatly. As the bias voltage approaches 0.050 mV (50 μV), the secondresistance R(AP) and the magneto-resistance ratio MR rapidly increase,going off the scale of FIG. 3. However, the first resistance R(P) doesnot vary greatly. As the bias voltage approaches 0 mV, the firstresistance R(P) varies rapidly. However, the variation of the firstresistance R(P) is much less than the variation of the second resistanceR(AP).

As the bias voltage applied to the magnetic film structure 30 of FIG. 1almost reaches 0.050 mV, the second resistance R(AP) suddenly becomesless than zero, and reaches a large negative value. Even in the examplewhere the second resistance R(AP) exhibits significant variation, thefirst resistance R(P) does not greatly and also does not exhibit thesame variation. As the bias voltage continues to approach 0 mV, thesecond resistance R(AP) rapidly increases to zero. At the bias voltageat which the second resistance R(AP) reaches from a large negative valueto zero, the first resistance R(P) exhibits some variation. However, asmentioned above, the variation of the first resistance R(P) is not largewhen compared to the variation of the second resistance R(AP).Accordingly, when the variation of the second resistance R(AP) iscompared with the variation of the first resistance R(P), the variationof the first resistance R(P) is negligible.

When the first resistance R(P) varies, it becomes negative for a shorttime, and then, when the bias voltage is 0 mV, the first resistance R(P)again becomes zero. After that, when the bias voltage becomes negative,the first resistance R(P) becomes again positive. When the bias voltageis 0 mV, even the second resistance R(AP) becomes zero (0), and thenwhen the bias voltage is negative, the second resistance R(AP) has apositive value, a little larger than zero. This state is maintained evenas the bias voltage decreases more. The variation of themagneto-resistance ratio MR of the magnetic film structure 30 generallyfollows the variation of the second resistance R(AP).

The magnetic film structure 30 exhibits the variation of the secondresistance R(AP) when the second resistance R(AP) rapidly increases atthe bias voltage between 0 mV and 0.1 mV, but does not exhibit avariation of the first resistance R(P) comparable to the variation ofthe second resistance R(AP). Accordingly, the magneto-resistance ratioMR of the magnetic film structure 30 is at least 200% at the biasvoltage between 0 mV and 0.1 mV, as shown in FIG. 3. Specifically, themagneto-resistance ratio MR has a large value moving away from ameasurement range at the bias voltage at which the second resistanceR(AP) has the variation change.

The potential difference between the lower magnetic film 42 and thefirst ferromagnetic film 46 causes the magnetic film structure 30 tohave a large magneto-resistance ratio MR. Since the magnetic filmstructure 30 can have a significant magneto-resistance ratio MR below0.3 mV, a semiconductor device including the magnetic film structure 30may exhibit reduced power consumption.

FIG. 4 illustrates a graph of resistance variation versus magnetic fieldof the magnetic film structure of FIG. 1 at a point P1 of FIG. 3. At thepoint P1 the bias voltage is about 0.088 mV (88 μV) and themagneto-resistance ratio is about 197%.

FIG. 5 illustrates a graph of resistance variation versus magnetic fieldof the magnetic film structure of FIG. 1 at a point P2 of FIG. 3. At thepoint P2 the bias voltage is about 0.016 mV (16 μV) and themagneto-resistance ratio is about −41%.

FIG. 6 illustrates a graph of resistance variation versus magnetic fieldof the magnetic film structure of FIG. 1 at a point P3 of FIG. 3. At thepoint P3 the bias voltage is about −0.089 mV (−89 μV) and themagneto-resistance ratio is about −10%.

FIG. 7 illustrates a graph of resistance variation depending on amagnetic field of the magnetic film structure of FIG. 1 at a point P4 ofFIG. 3. At the point P4 the bias voltage is about −0.171 mV (−171 μV)and the magneto-resistance ratio is about −2%.

In Table 1, below, the magneto-resistance ratio of the magnetic filmstructure 30 is summarized for several bias voltages, with reference toFIG. 3.

TABLE 1 Bias voltage (μV) Magneto-resistance ratio (%) 64 760 70 380 76240 88 170 98 130 106 110 117 94 126 85 137 78

FIG. 8 illustrates a graph of resistance variation of the magnetic filmstructure of FIG. 1 versus magnetic field for a plurality of biasvoltages. In FIG. 8, a reference symbol “□” denotes the resistancevariation of the magnetic film structure 30 versus the external magneticfield when a bias voltage of 64 μV is applied to the magnetic filmstructure 30. A reference symbol “∘” denotes a resistance variation whena bias voltage of 70 μV is applied. A reference symbol “Δ” denotes aresistance variation when a bias voltage of 76 μV is applied. Areference symbol “∇” denotes a resistance variation when a bias voltageof 88 μV is applied. A reference symbol “⋄” denotes a resistancevariation when a bias voltage of 98 μV is applied. A reference symbol

denotes a resistance variation when a bias voltage of 106 μV is applied.A reference symbol

denotes a resistance variation when a bias voltage of 117 μV is applied.A black hexagon denotes a resistance variation when a bias voltage of126 μV is applied. A pentagon denotes a resistance variation when a biasvoltage of 137 μV is applied.

FIG. 9 illustrates a graph of resistance variation of the magnetic filmstructure of FIG. 1 versus magnetic field at a bias voltage of 55 mV.Referring to FIG. 9, when the magnetic field is more than zero, themagnetic film structure 30 has the lowest resistance. When the magneticfield is less than zero, the resistance of the magnetic film structure30 rapidly increases to be as large as at least six times the lowestresistance.

Two methods may be employed for applying a bias voltage to the magneticfilm structure 30. In a first method, the bias voltage may be applied tothe magnetic film structure 30 such that a current flows from the firstferromagnetic film 46 to the lower magnetic film 42 (actually, electronsflow from the lower magnetic film 42 to the first ferromagnetic film46), as illustrated in FIG. 10. A second method may be performedoppositely to the first method, as illustrated in FIG. 11.

FIGS. 12 and 13 illustrate current-voltage characteristics of themagnetic film structure 30. FIG. 12 illustrates a graph ofcurrent-voltage characteristic of the magnetic film structure of FIG. 1to which a bias voltage is applied according to the first method, asillustrated in FIG. 10. FIG. 13 illustrates a graph of a current-voltagecharacteristic of the magnetic film structure of FIG. 1 to which a biasvoltage is applied according to the second method, as illustrated inFIG. 11

In FIG. 12, a graph G11 illustrates the current-voltage characteristicmeasured when the lower magnetic film 42 and the first ferromagneticfilm 46 of the magnetic film structure 30 have the same magnetizationdirection. Additionally, a graph G22 illustrates the current-voltagecharacteristic measured when the lower magnetic film 42 and the firstferromagnetic film 46 have opposite magnetization directions to eachother.

Referring to the graphs G11 and G22, in a case where the lowermagnetization film 42 and the first ferromagnetic film 46 have the samemagnetization direction (hereinafter, referred to as “the first case”),when the bias voltage is zero, the current is also zero. However, in acase where the lower magnetization film 42 and the first ferromagneticfilm 46 have the opposite magnetization directions to each other(hereinafter, referred to as “the second case”), when the bias voltageis zero, the current is not zero. In the second case, when the biasvoltage is −0.050 mV, the current becomes zero. In other words, the biasvoltage at which the current is zero in the second case is shifted tothe left by about −0.050 mV.

A material characteristic of the magnetic film structure 30 may varydepending on the materials constituting the magnetic film structure 30,the size of the magnetic film structure 30 and/or the temperature of themagnetic film structure 30. Therefore, the degree of shift of the biasvoltage in the second case may depend on the material constituting thelower magnetic film 42 and/or the first ferromagnetic film 46, and maydepend on the size and/or temperature of the films 42 and 46. This isillustrated in FIG. 13, a case in which the bias voltage at which thecurrent becomes zero is shifted to the right.

A graph G31 of FIG. 13 illustrates a current-voltage characteristic inthe first case, and is the same as the graph G11 of FIG. 12. A graph G32of FIG. 13 illustrates a current-voltage characteristic in the secondcase. Referring to the second graph G32, when the magnetic filmstructure 30 is in the second case and the bias voltage is applied tothe magnetic film structure 30, as shown in FIG. 10, the current becomeszero at the bias voltage of 0.050 mV(50 μV), not 0 mV. In other words,the bias voltage at which the current becomes zero may be shifted to theright. As a result, when the magnetic film structure 30 is in the secondcase, the bias voltage at which the current becomes zero may be shifted.This may be achieved using any method, although the bias voltage mayhave a different shift direction.

The shift of the bias voltage at which the current becomes zero when themagnetic film structure 30 is in the second case occurs because of thepotential difference caused by the electrochemical potential between thelower magnetic film 42 and the first ferromagnetic film 46. In otherwords, even though the bias voltage of 0 mV is applied, e.g., in theexample where the potential difference exists between the lower magneticfilm 42 and the first ferromagnetic film 46, the current of the magneticfilm structure 30 does not become zero. Thus, a current derived from thepotential difference may be measured from the magnetic film structure30.

However, as the bias voltage (hereinafter, referred to as “the shiftvoltage”) having a magnitude corresponding to the potential differenceis applied to the magnetic film structure 30, charges may be eliminatedfrom the interface of the lower magnetic film 42 and the firstferromagnetic film 46, such that the potential difference no longerexists between the lower magnetic film 42 and the first ferromagneticfilm 46. In other words, where the shift voltage and the potentialdifference offset each other, the current measured from the magneticfilm structure 30 will go to zero. The potential difference between thelower magnetic film 42 and the first ferromagnetic film 46 may beeliminated at the shift voltage, so that the current of the magneticfilm structure 30 becomes zero. Therefore, the shift voltage becomes theoffset voltage.

The offset voltage of the magnetic film structure 30 may be defined as adifference of the bias voltage at which the current becomes zero is inthe first case and the bias voltage at which the current becomes zero inthe second case. That is, the offset voltage may equal the shiftvoltage. However, the bias voltage at which the current becomes zero isvery close to 0 mV when the magnetic film structure 30 is in the firstcase, as illustrated in FIGS. 12 and 13. Accordingly, the shift voltagemay be regarded as the offset voltage.

The potential difference existing between the lower magnetic film 42 andthe first ferromagnetic film 46 may be caused by the electrochemicalpotential difference between the lower magnetic film 42 and the firstferromagnetic film 46. Accordingly, the measurement of the offsetvoltage may essentially be a measurement of the electrochemicalpotential difference between the lower magnetic film 42 and the firstferromagnetic film 46.

Since the current is zero at the offset voltage, the resistance isinfinite, according to the equation R=V/I. Accordingly, when themagnetic film structure 30 is in the second case, the bias voltage isclose to the offset voltage while the resistance and themagneto-resistance ratio vary (FIG. 3).

The offset voltage of the magnetic film structure 30 varies with a sizeof the magnetic film structure 30. In detail, as the size of themagnetic film structure 30 is increased, the offset voltage isdecreased. If the size is more than a predetermined value, the voltageshift is not shown in the graph of the current-voltage characteristic.This means that when the voltage shift is not generated, the offsetvoltage is zero. The properties are illustrated in FIGS. 14-17.

FIGS. 14-17 illustrate results respectively measured when the lowermagnetic film 42 of the magnetic film structure 30 is formed under thesecond condition (20 mTorr, 600° C.) and the magnetic film structure 30has the sizes of 10 μm×10 μm (FIG. 14), 30 μm×30 μm (FIG. 15), 50 μm×50μm (FIGS. 16) and 100 μm×100 μm (FIG. 17).

In FIGS. 14-17, a reference symbol “□” denotes a current-voltagecharacteristic measured in the first case and a reference symbol “∘”denotes a current-voltage characteristic measured in the second case.Referring to FIGS. 14 to 17, when the magnetic film structure 30 has thesizes of 10 μm×10 μm and 30 μm×30 μm, the offset voltage isapproximately 27 μV. However, when size is 50 μm×50 μm, the offsetvoltage is smaller, about 14 μV, as illustrated in FIG. 16.Additionally, when the size is 100 μm×100 μm, the offset voltage becomes0 μV, as illustrated in FIG. 17.

A resistor may be connected to the magnetic film structure 30. Acurrent-voltage characteristic of this scenario is illustrated in FIG.18. Referring to FIG. 18, even where the resistor is connected, anoffset voltage may be generated, although it may be smaller than whenthe resistor is not connected.

A temperature dependency of the offset voltage will now be described.Equation 1 is theoretically obtained from the offset voltage and thetemperature of the magnetic film structure 30 shown in FIG. 1.

Vd=(8.4×10⁻⁵)η²(Ie/A)C^(1/2)(1/T ^(1/4))   Equation 1:

In Equation 1, Ie is electron current, η is spin deflection current, Ais cross section, C is current degree and T is absolute temperature. Theoffset voltage Vd is proportional to T^(1/4).

In order to verify whether or not the temperature dependency of themagnetic film structure 30 actually satisfies Equation 1, the offsetvoltage for the magnetic film structure 30 may be measured, e.g., attemperatures ranging from 50K to 300K, at which phonon scattering isdominant. This measurement result is illustrated in FIG. 19. Referringto FIG. 19, when the temperature T ranges from 50K to 300K, the offsetvoltage is proportional to T^(1/4). However, this is not so at T=5K,where a residual resistance effect is dominant. Thus, a theoreticalresult and an experimental result for the temperature dependency of theoffset voltage are consistent with each other when the temperature T ofthe magnetic film structure 30 is a range of at least 50K to 300K.

In a magnetic film structure 30 having the above-described physicalcharacteristic, positions of the half-metal ferromagnetic film 42 andthe upper magnetic film 45 may be reversed. For example, as shown inFIG. 20, the half-metal ferromagnetic film 42 may be provided on thetunneling film 44 and the upper magnetic film 45 may be provided underthe tunneling film 44. The first ferromagnetic film 46 of the uppermagnetic film 45 may be in contact with the tunneling film 44 and thesecond ferromagnetic film 48 may be positioned under the firstferromagnetic film 46.

A manufacturing method of the magnetic film structure 30 of FIG. 1 willnow be described. Referring to FIG. 21, a thin insulating film 38 may beformed on a substrate 36, e.g., a silicon substrate. The insulating film38 may be formed of oxide or nonoxide. Where the substrate 36 is asilicon substrate, the insulating film 38 may be formed of siliconoxide, but it may also be formed of other oxides. The silicon oxide filmmay be grown using a thermal growth method. A seed layer 40 may beformed on the insulating film 38. The seed layer 40 may help promote thegrowth of a lower magnetic film 42, and may help smooth a surface of thelower magnetic film 42 to help form a tunneling film 44 to a regularthickness. The lower magnetic film 42 may be formed on the insulatingfilm 38.

The lower magnetic film 42 may be formed of a predetermined compoundferromagnetic material, e.g., a half-metal ferromagnetic (HMF) material.In this description, the lower magnetic film 42 will be described as thehalf-metal ferromagnetic film 42.

Where the magnetic film structure 30 is to be used as a magnetic tunneljunction layer of a magnetic random access memory (MRAM), the half-metalferromagnetic film 42 may be used as a free layer, in which amagnetization direction, i.e., a spin polarization, is changed by anexternal magnetic field.

The seed layer 40 may be formed using, e.g., a sputtering method orother deposition methods. The seed layer 40 may be formed bysequentially depositing first and second seed layers 40 a and 40 b. Theseed layer 40 may be formed as a magnetic layer, a nonmagnetic layer, ora combination of the magnetic layer and the nonmagnetic layer. Where theseed layer 40 is formed as a nonmagnetic layer, the first and secondseed layers 40 a and 40 b may be respectively formed of, e.g., tantalum(Ta) and ruthenium (Ru). In this example, the first seed layer 40 a maybe formed to thickness of, e.g., about 42 nm, and the second seed layer40 b may be formed to a thickness of, e.g., about 9.5 nm. Where thefirst and second seed layers 40 a and 40 b are formed using othermaterial layers, they may have different thicknesses from theabove-described thicknesses.

After the seed layer 40 is formed, the half-metal ferromagnetic film 42may be deposited on the seed layer 40. The half-metal ferromagnetic film42 may be the lower magnetic film. The half-metal ferromagnetic film 42may be formed of a ferromagnetic material having a spin polarizationratio of 80% to 100%. Also, the half-metal ferromagnetic film 42 may beformed of a ferromagnetic material having a higher spin polarizationratio than the upper magnetic film 45. The half-metal ferromagnetic film42 may be formed of, e.g., Co₂MnSi. Co₂MnSi is a Heusler alloy and isfound to be a half-metal ferromagnetic film in a calculation of a bandstructure. Where the half-metal ferromagnetic film 42 is a Co₂MnSi film,the half-metal ferromagnetic film 42 may be formed to have apredetermined thickness of, e.g., about 47 nm. Where the half-metalferromagnetic film 42 is formed of other materials, the half-metalferromagnetic film 42 may have different thicknesses.

In order to form the half-metal ferromagnetic film 42 with improvedcrystallinity, the substrate 36 may be maintained at a predeterminedtemperature, e.g., above about 500° C., or between 500° C. to 600° C.The half-metal ferromagnetic film 42 may be formed at a low pressure,for example, at 5×10⁻⁸ Torr. The half-metal ferromagnetic film 42 may beformed using, e.g., deposition, sputtering, etc., while maintaining theabove-described temperature and pressure conditions. Where the seedlayer 40 and the half-metal ferromagnetic film 42 are all formed usingsputtering, the seed layer 40 and the half-metal ferromagnetic film 42may be formed in situ using the same sputtering equipment.

The roughness of half-metal ferromagnetic film 42 may be reduced by,e.g., suitably controlling related variables such as a radio frequency(RF) power or a pressure. Accordingly, the tunneling film 44 may beformed to a regular thickness on the half-metal ferromagnetic film 42.

After the half-metal ferromagnetic film 42 is formed, the tunneling film44 may be formed on the half-metal ferromagnetic film 42. The tunnelingfilm 44 may be formed of oxide, e.g., aluminum oxide—alumina (Al₂O₃),and may be also formed of nonoxide. Where the tunneling film 44 isaluminum oxide, the tunneling film 44 may be, e.g., about 1.5 nm thick.Where the tunneling film 44 is formed of oxides other than aluminumoxide, or nonoxide, the tunneling film 44 may be formed at a differentthickness. Further, where the tunneling film 44 is formed of aluminumoxide, the tunneling film 44 may be formed using, e.g., sputtering, inthe same manner as the seed layer 40 and the half-metal ferromagneticfilm 42.

In detail, after the half-metal ferromagnetic film 42 is formed usingsputtering equipment, the sputtering equipment may be cooled to a roomtemperature. Aluminum film may then be deposited at a predeterminedthickness on the half-metal ferromagnetic film 42 in the cooledsputtering equipment. The deposited aluminum film may then be oxidizedusing a plasma oxidation process to form the aluminum oxide film on thehalf-metal ferromagnetic film 42. The plasma oxidation process may beperformed in the sputtering equipment, or in other equipment. Where theplasma oxidation process is performed using the sputtering equipment,the sputtering equipment may be maintained with an atmosphere of pureoxygen and a pressure of 150 mTorr until the plasma oxidation process iscompleted.

After the tunneling film 44 is formed, the upper magnetic film 45 may beformed on the tunneling film 44. The upper magnetic film 45 may beformed using, e.g., sputtering or other deposition processes. The uppermagnetic film 45 may be formed by sequentially depositing first andsecond ferromagnetic films 46 and 48. The first ferromagnetic film 46may have a magnetization direction corresponding to a direction of thesecond ferromagnetic film 48. The first ferromagnetic film 46 may beformed of, e.g., CoFe or of other ferromagnetic materials, and may havea different thickness depending on the material. For example, where thefirst ferromagnetic film 46 is formed of cobalt iron, the firstferromagnetic film 46 may be about 7.5 nm thick, although the firstferromagnetic film 46 may be formed of other materials and may be formedthicker or thinner.

The second ferromagnetic film 48 may be a pinning film for establishingthe magnetization direction of the first ferromagnetic film 46. Thesecond ferromagnetic film 48 may be formed as, e.g., a single film or amulti-layer film. Where the second ferromagnetic film 48 is a singlefilm, it may be formed to a predetermined thickness using, e.g., an antiferromagnetic film (AFM) such as an iridium manganese (IrMn) film about15.5 nm thick. Where the second ferromagnetic film 48 is a multi-layerfilm, the second ferromagnetic film 48 may be formed using, e.g., asynthetic anti-ferromagnetic (SAF) film having a conductive film and amagnetic film provided on and under the conductive film. Themagnetization direction of the first ferromagnetic film 46 may beestablished by an exchange bias effect or an interlayer coupling throughthe SAF film.

After the upper magnetic film 45 is formed, a capping layer 49 may beformed on the upper magnetic film 45 to prevent the oxidation of theupper magnetic film 45, especially, the oxidation of the secondferromagnetic film 48. The capping layer 49 may be formed using, e.g.,the sputtering process described above, which may be at roomtemperature, or using other deposition processes. Where the cappinglayer 49 is formed using sputtering, the capping layer 49 may be formedin situ after the upper magnetic film 45 is formed. The capping layer 49may be, e.g., ruthenium (Ru) having a thickness of 60 nm, although thecapping layer 49 may be formed of different materials and to differentthicknesses.

Next, a photosensitive film pattern M1 may be formed on the cappinglayer 49 to define a predetermined region of the capping layer 49. Thedefined region of the capping layer 49 may have a size of, e.g., 10μm×10 μm and may be extended to allow for the observation of the offsetvoltage. For example, the defined region may be extended to have a sizeof 30 μm×30 μm, 50 μm×50 μm, etc. Further, the defined region need nothave a square shape and may have different length sides.

The photosensitive film pattern M1 may be used as an etching mask toetch the capping layer 49 at a periphery of the photosensitive filmpattern Ml. The etching may be performed until the substrate 36 isexposed. The photosensitive film pattern M1 may then be eliminated.Thus, the magnetic film structure 30 of FIG. 1 may be formed on thesubstrate 36 as shown in FIG. 22. Further, in the above-mentionedmanufacturing method, the positions of the half-metal ferromagnetic film42 and the upper magnetic film 45 may be changed with respect to eachother.

FIG. 23 illustrates a transmission electron microscopy (TEM) image of auniform thickness tunneling film of the magnetic film structure of FIG.1 formed through the manufacturing method illustrated in FIGS. 21 and22. Referring to FIG. 23, the tunneling film 44 may exhibit a regularthickness.

A semiconductor device having the magnetic film structure 30 of FIG. 1,e.g., a semiconductor memory device, will now be described. FIG. 24illustrates a cross-sectional view of a magnetic RAM according to thepresent invention, in which the magnetic film structure of FIG. 20 isused as a magnetic tunnel junction (MTJ) layer. Referring to FIG. 24,the MRAM may have first and second impurity regions 72, 74, formed bydoping conductive impurities into a semiconductor substrate 70. Achannel region 75 may be formed in the semiconductor substrate 70between the first and second impurity regions 72 and 74. The firstimpurity region 72 may be a source region or a drain region. The secondimpurity region 74 may also be a source region or a drain region. Adeposited gate material 76 may be formed on the channel region 75between the first and second impurity regions 72 and 74. The depositedgate material 76 may include a gate insulating film (not shown), a gateelectrode (not shown) and a gate spacer (not shown). The semiconductorsubstrate 70, the first and second impurity regions 72 and 74, thechannel region 75 and the deposited gate material 76 may constitute afield effect transistor (FET).

An interlayer insulating layer 78 may be formed on the semiconductorsubstrate 70 to cover the first and second impurity regions 72 and 74and the deposited gate material 76. A contact hole 80 may be provided inthe interlayer insulating layer 78 to expose the first impurity region72. The contact hole 80 may be filled with a conductive plug 82. Theconductive plug 82 and the first impurity region 72 may be in ohmiccontact with each other to reduce a contact resistance. A pad conductivelayer 84 may be formed on the interlayer insulating layer 78 to beconnected to the conductive plug 82. The pad conductive layer 84 may beextended over the deposited gate material 76. A digit line 77 may beformed in the interlayer insulating layer 78 between the pad conductivelayer 84 and the deposited gate material 76. The digit line 77 may beused to generate the magnetic field for recording data in the MTJ layer86 (described later). The MTJ layer 86 may be provided on the padconductive layer 84. The MTJ layer 86 may be provided over the digitline 77.

The MTJ layer 86 may be the magnetic film structure 30 of FIG. 1. Aninterlayer insulating layer 88 may be formed on the interlayerinsulating layer 78 to cover the MTJ layer 86. A via hole 90 may beprovided in the interlayer insulating layer 88 to expose the MTJ layer86. The via hole 90 may be filled with a conductive plug 91. A bit line92 may be formed on the interlayer insulating layer 88 to be connectedto the conductive plug 91. The bit line 92 may be used together with thedigit line 77 to record data in the MTJ layer 86. In other words, adirection of a current flowing through the bit line 92 and the digitline 77 may be controlled to control the magnetization direction of thehalf-metal ferromagnetic film (e.g., feature 42 of FIG. 1) of the MTJlayer 86.

The above-described MRAM may be formed using a general MRAMmanufacturing process. However, the MTJ layer 86 may also be formedusing a manufacture method of the magnetic film structure 30.

An operation method of the MRAM illustrated in FIG. 24 will now bedescribed. At this time, the MTJ layer 86, which may be used as the datastoring unit, of the MRAM is assumed to include the half-metalferromagnetic film 42 provided on the tunneling film 44, as illustratedin FIG. 20.

<Writing>

Referring to FIGS. 24-26, a current may be supplied to the digit line 77and the bit line 92 in the given direction. At this time, a magneticfield is generated at the digit line 77 and the bit line 92. Themagnetic field (hereinafter, referred to as “external magnetic field”)causes the spin polarization of the electrons of the half-metalferromagnetic film 42, which is the free layer of the MTJ layer 86, tobe arranged in a direction of the external magnetic field. The result ofthe arrangement is illustrated with the half-metal ferromagnetic film 42magnetized in the direction of the magnetic field.

FIG. 25 illustrates a cross-sectional view of a MTJ layer in whichmagnetic films have the same magnetization direction on and under atunneling film in the magnetic RAM of FIG. 24. FIG. 26 illustrates across-sectional view of a MTJ layer in which magnetic films haveopposite magnetization directions to each other on and under a tunnelingfilm in the magnetic RAM of FIG. 25. That is, FIG. 25 illustrates anexample in which the external magnetic field has the same magnetizationdirection as the first ferromagnetic film 46, while FIG. 26 illustratesan example in which the external magnetic field has the oppositemagnetization direction to the first ferromagnetic film 46.

As illustrated in FIG. 25, in the example where the magnetizationdirection of the half-metal ferromagnetic film 42 is the same as that ofthe first ferromagnetic film 46 due to the external magnetic field, data“0” is recorded in the magnetic RAM. As illustrated in FIG. 26, in theexample where the magnetization direction of the half-metalferromagnetic film 42 is opposite to that of the first ferromagneticfilm 46 due to the external magnetic field, data “1” is recorded in themagnetic RAM. Of course, data “0” and “1” may be recorded oppositely.

In the example where data “1” is recorded in the magnetic RAM, for thesame reason described in the descriptions of the magnetic film structure30 of FIG. 1, the positive charges (+) are collected at an interface ofthe first ferromagnetic film 46 contacting with the tunneling film 44and the negative charges (−) are collected at an interface of thehalf-metal ferromagnetic film 42 contacting with the tunneling film 44.As a result, in the example where data “1” is recorded in the magneticRAM, a potential difference is formed between the half-metalferromagnetic film 42 and the first ferromagnetic film 46.

<Reading>

Where data “0” is recorded in the inventive magnetic RAM in a stateshown in FIG. 25, a transistor is turned on and a resistance of the MTJlayer 86 may be measured to read data “0” recorded in the MTJ layer 86.

Where data “1” is recorded in the inventive magnetic RAM in a stateshown in FIG. 26, data “1” may be read from the MTJ layer 86 by a numberof methods, e.g., the resistance of the MTJ layer 86 may be measured,the shift voltage (i.e., the offset voltage) may be measured, or thecurrent caused by the potential difference between the half-metalferromagnetic film 42 and the first ferromagnetic film 46 may bemeasured.

In the example where data “1” is read in by measuring the current causedby the potential difference, the external magnetic field may be used toinvert the magnetization direction of the half-metal ferromagnetic film42 into the same direction as the first ferromagnetic film 46. Where themagnetization direction of the half-metal ferromagnetic film 42 isinverted into the same direction of the first ferromagnetic film 46, thecharges collected at the interfaces of the half-metal ferromagnetic film42 and the first ferromagnetic film 46 contacting with the tunnelingfilm 44 flow through the transistor, which acts as a switching element.Therefore, the current may be sensed using a sensor amplifier connectedto the second impurity region 74 of the transistor.

However, after data “1” is read by this method, the charges are alleliminated at the interfaces of the half-metal ferromagnetic film 42 andthe first ferromagnetic film 46 with the tunneling film 44. Therefore,in order to maintain original data “1”, the magnetization direction ofthe half-metal ferromagnetic film 42 may be inverted into the oppositemagnetization direction to that of the first ferromagnetic film 46 afterdata “1” is read. This may be accomplished by inverting the direction ofthe external magnetic field.

<Erasing>

After the transistor of FIG. 24 is turned off, the magnetizationdirections of the half-metal ferromagnetic film 42 and the firstferromagnetic film 46 are allowed to be identical. That is, themagnetization direction of the half-metal ferromagnetic film 42 may beinverted to be the same as the magnetization direction of the firstferromagnetic film 46. The magnetization direction of the half-metalferromagnetic film 42 may be inverted by the magnetic field generatedfrom the bit line 92 and the digit line 77.

The magnetic film structure 30 may be also applied to othersemiconductor devices. For example, FIG. 27 illustrates across-sectional view of a magnetic film structure 30 used as a magneticsensor 110 of a magnetic head 100. In FIG. 27, reference numeral 120denotes a magnetic recording media and reference numerals D1-D5 denotedomains of the magnetic recording media 120. Referring to FIG. 27, wherethe magnetic sensor 110 of the head 100 is proximal to the magneticrecording media 120, e.g., to read data from the magnetic recordingmedia 120, the magnetization direction of the half-metal ferromagneticfilm 110 a of the magnetic sensor 110 may be influenced by themagnetization direction of the first to fifth domains (D1, . . . , D5)of the magnetic recording media 120.

For example, an initial magnetization direction of a half-metalferromagnetic film 110 a of the magnetic sensor 110 and themagnetization direction of a pinning film 110 c point left on thedrawing, and magnetization directions of the first to fifth domainsD1-D5 point right, right, left, right and left, respectively. In thisstate, in the example where the magnetic sensor 110 is moved from thefirst domain D1 to the fifth domain D5, the magnetization direction ofthe half-metal ferromagnetic film 110 a is inverted and points right onthe first domain D1. Accordingly, the resistance of the magnetic sensor110 is increased. The magnetization direction of the half-metalferromagnetic film 110 a is maintained, pointing to the right, on thesecond domain D 2, and the magnetization direction of the half-metalferromagnetic film 110 a is inverted, pointing to the left, on the thirddomain D3. Accordingly, when the half-metal ferromagnetic film 110 a ispositioned on the third domain D3, the resistance of the magnetic sensor110 is lowered. When the magnetic sensor 110 is positioned on the fourthdomain D4, the magnetization direction of the half-metal ferromagneticfilm 110 a is inverted to point the right, which increases theresistance of the magnetic sensor 110. When the magnetic sensor 110passes the fourth domain D4 and is positioned on the fifth domain D5,the magnetization direction of the half-metal ferromagnetic film 110 ais inverted to point to the left and lower the resistance of themagnetic sensor 110. As such, the resistance of the magnetic sensor 110may be different depending on the magnetization direction of each domainof the magnetic recording media 120. Therefore, this may be used to reada magnetization state of each domain of the magnetic recording media120, i.e., data recorded in each domain of the magnetic recording media120.

As described above, in the magnetic film structure 30, the charges arecaused by the electrochemical potential difference of the twoferromagnetic films at facing surfaces of the two ferromagnetic filmswhen the magnetization direction of the half-metal ferromagnetic film isopposite to the magnetization direction of the ferromagnetic film. Themagnetization direction may be changed by the external magnetic field.The magnetization direction of the ferromagnetic film may be apredetermined direction. Accordingly, a potential difference may beformed between the two magnetic films, and the potential differencecauses the current-voltage characteristic curve of the magnetic filmstructure to be shifted by a given value. That is, an offset voltage isobserved in the current-voltage characteristic curve. Additionally, themagnetic resistance ratio of the magnetic film structure is rapidlyincreased at a periphery of the offset voltage.

Accordingly, according to the magnetic film structure 30, a highmagnetic resistance ratio may be obtained at a low voltage. Where themagnetic film structure 30 is used for a semiconductor memory device,e.g., a magnetic RAM, power consumption may be not only reduced, butalso data may be clearly and exactly read due to a high magneticresistance ratio. Further, the magnetic film structure may have asmaller size. Therefore, a semiconductor device, e.g., a logic device,having the magnetic film structure 30 may have an increased degree ofintegration and reduced power consumption. Further, the magnetic filmstructure 30 may exhibit a potential difference, and the potentialdifference may be provided by changing the magnetization direction ofthe half-metal ferromagnetic film to be opposite to the magnetizationdirection of the ferromagnetic film. Therefore, the inventive magneticfilm structure 30 may be integrated and used as a rechargeable battery.The magnetic film structure 30 of FIG. 1 or FIG. 20 may also be appliedto a logic device, e.g., an inverter, etc. Further, a half-metalferromagnetic film which has a semiconductor component other thansilicon (Si), e.g., germanium (Ge), may be used and a half-metalferromagnetic film, e.g., one which has copper (Cu) instead of cobalt,may be also used.

Exemplary embodiments of the present invention have been disclosedherein, and although specific terms are employed, they are used and areto be interpreted in a generic and descriptive sense only and not forpurpose of limitation. Accordingly, it will be understood by those ofordinary skill in the art that various changes in form and details maybe made without departing from the spirit and scope of the presentinvention as set forth in the following claims.

1-21. (canceled)
 22. A method of operating a semiconductor memorydevice, the semiconductor memory device including a substrate, aswitching element formed on the substrate, and a data storing unitconnected to the switching element, wherein the data storing unitincludes a lower magnetic film, a tunneling film formed on the lowermagnetic film and an upper magnetic film formed on the tunneling film,the method comprising: applying, in a state where the switching elementis turned off, a magnetic field to the data storing unit in a givendirection to record data in the data storing unit; wherein the lower andupper magnetic films are ferromagnetic films forming an electrochemicalpotential difference therebetween when the lower and upper magneticfilms have opposite magnetization directions.
 23. The method as claimedin claim 22, wherein, in a state where the switching element is turnedon, an offset voltage of the data storing unit is measured to read datafrom the data storing unit.
 24. The method as claimed in claim 22,wherein data recorded in the data storing unit is read by applying themagnetic field to the data storing unit such that the upper and lowermagnetic films have the same magnetization direction in the state wherethe switching element is turned on, and sensing whether a current ofmore than a first value flows through the data storing unit.
 25. Themethod as claimed in claim 24, wherein a magnetization state of a firstof the upper and lower magnetic films is restored to an original stateif the current of more than the first value is sensed, the first of theupper and lower magnetic films being one of the upper and lower magneticfilms whose magnetization state is varied by the magnetic field appliedto read recorded data.
 26. The method as claimed in claim 25, wherein amagnetic field having an opposite direction to the magnetic fieldapplied to read recorded data is applied to restore the magnetizationstate of the first of the upper and lower magnetic films to the originalstate.
 27. The method as claimed in claim 22, wherein, in the statewhere the switching element is turned off, the upper and lower magneticfilms are allowed to have the same magnetization direction to erase datafrom the data storing unit.
 28. The method as claimed in claim 22,wherein at least one of the upper and lower magnetic films is ahalf-metal ferromagnetic film.
 29. The method as claimed in claim 28,wherein the half-metal ferromagnetic film has a spin polarization ratioof 80% to 100%.
 30. The method of claim 22, wherein the data storingunit has a size of less than 100 μm².
 31. The method as claimed in claim22, wherein the data storing unit further includes a capping layerformed on the upper magnetic film.
 32. The method as claimed in claim22, wherein the lower magnetic film includes a first ferromagnetic filmformed to contact the tunneling film and a second ferromagnetic filmformed under the first ferromagnetic film.